The movement of proteins across the digestive system of tobacco budworm, Heliothis virescens

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Title: The movement of proteins across the digestive system of tobacco budworm, Heliothis virescens
Author: Jeffers, Laura Ann
Advisors: Randy L. Rose, Committee Member
Charles S. Apperson, Committee Member
R. Michael Roe, Committee Chair
Abstract: Bovine serum albumin (BSA) and anti-BSA polyclonal antibody were used as model polypeptides to examine protein movement across the insect digestive system and cuticle and their accumulation in hemolymph of fourth stadium tobacco budworms, Heliothis virescens. The use of hydrateable meal pads to deliver a specific concentration of these two proteins in insect diet was investigated. Continuous feeding on artificial diet containing 0.8 mg of anti-BSA/g hydrated diet resulted in 2430±125 and 3459±105 ng of anti-BSA/mL hemolymph after 8 and 16 h, respectively (average ± 1 SEM), as determined by ELISA. Continuous feeding on meal pads with the same concentration of BSA resulted in 1547±132 and 1623±122 ng of BSA/mL hemolymph at 8 and 16 h, respectively. No BSA or anti-BSA was found in the feces, and when 5 mg of these two proteins were applied topically in DMSO to the cuticle, neither protein was found in the hemolymph after 4 h. Western blot analyses using native and/or de-naturing gel electrophoresis demonstrated that both BSA and anti-BSA were not degraded in the hydrated meal pads and were also unchanged in the hemolymph, retaining the multimeric structure for BSA and the antigen reactivity for anti-BSA. When 1 mg of anti-BSA or BSA was injected into the hemocoel of fourth instars, the concentrations decreased with time and 120 min after injection were 0.6 and 20% of the original concentration, respectively. When added at the same original concentration to hemolymph in vitro, the decrease was 81.5 and 57.5%, respectively, at 120 min. Apparently, the accumulation of native anti-BSA and BSA protein in insect hemolymph is the result of the rate of their transfer from the diet versus their rate of turnover in the hemolymph. Hemolymph turnover of these proteins appears to be the result of degradation and sequestration.
Date: 2004-02-23
Degree: MS
Discipline: Entomology

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